The present invention relates to refrigerated merchandisers, and more particularly to a control system for refrigerated merchandisers.
Refrigerated merchandisers are used by grocers to store and display food items in a product display area that must be kept within a predetermined temperature range. These merchandisers generally include a case that is conditioned by a refrigeration system that has a compressor, a condenser, and at least one evaporator connected in series with each other. At low operating temperatures, frost often forms on the evaporator, especially near the air inlet to the heat exchanger. Such frost formation can damage the evaporator and necessitate relatively frequent and thorough defrost cycles.
Both open and closed merchandisers require regular defrost cycles to maintain the coil sufficiently free of ice build-up such that it can perform to its intended purpose and capacity. However, the defrost cycles add heat to the product display area, which shortens product shelf life and increases the refrigeration load needed to cool product to the desired temperature. It is common for existing medium temperature merchandisers to have four to eight defrost cycles within a 24 hour period. For existing low temperature merchandisers, it is common to have one to four defrost cycles within a 24 hour period.